package com.lagou.sqlSession;

import com.lagou.config.BoundSql;
import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;
import com.lagou.utils.GenericTokenParser;
import com.lagou.utils.ParameterMapping;
import com.lagou.utils.ParameterMappingTokenHandler;
import com.lagou.utils.TokenHandler;

import java.beans.PropertyDescriptor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class SimpleExecutor implements Executor {


    @Override
    public <E> List<E> query(Configuration configuration, MappedStatement mappedStatement, Object... params) throws Exception {
        // 1. 注册驱动，获取连接
        Connection connection = configuration.getDataSource().getConnection();

        // 2. 获取sql 语句
        String sql = mappedStatement.getSql();
        // 3. 转换sql 语句
        BoundSql boundSql = getBoundSql(sql);

//        3. 获取预处理对象：preparedStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());
        // 4. 设置参数
        //  获取到了参数的全路径
        String paramterType = mappedStatement.getParamterType();
        Class<?> paramTypeclass = getClassType(paramterType);
        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for(int i=0;i<parameterMappingList.size(); i++){
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();

            // 反射
            Field declaredField = paramTypeclass.getDeclaredField(content);
            // 暴力访问
            declaredField.setAccessible(true);
            Object o = declaredField.get(params[0]);
            preparedStatement.setObject(i+1,o);
        }
        // 5.执行sql
        ResultSet resultSet = preparedStatement.executeQuery();
        String resultType = mappedStatement.getResultType();
        Class<?> resultclassType = getClassType(resultType);
        // 存储结果容器
        ArrayList<Object> result = new ArrayList<>();
        // 封装返回结果集
        while(resultSet.next()){
            Object o = resultclassType.newInstance();
            // 元数据
            ResultSetMetaData metaData = resultSet.getMetaData();
            for(int i=1;i<=metaData.getColumnCount();i++){
                // 字段名
                String columnName = metaData.getColumnName(i);
                // 字段值
                Object value = resultSet.getObject(columnName);

                //使用反射或者内容，根据数据库表和实体的对应关系，完成封装
                PropertyDescriptor propertyDescriptor = new PropertyDescriptor(columnName, resultclassType);
                Method writeMethod = propertyDescriptor.getWriteMethod();
                writeMethod.invoke(o,value);
            }
            result.add(o);
        }
        return (List<E>)result;

    }

    /**
     *  执行增删改的公共方法
     * @param configuration
     * @param mappedStatement
     * @param params
     * @param <T>
     * @return
     */
    private <T> T execute(Configuration configuration, MappedStatement mappedStatement, Object... params) throws SQLException, ClassNotFoundException, NoSuchFieldException, IllegalAccessException, InstantiationException {
        // 1. 注册驱动，获取连接
        Connection connection = configuration.getDataSource().getConnection();

        // 2. 获取sql 语句
        String sql = mappedStatement.getSql();
        // 3. 转换sql 语句
        BoundSql boundSql = getBoundSql(sql);

//        3. 获取预处理对象：preparedStatement
        PreparedStatement preparedStatement = connection.prepareStatement(boundSql.getSqlText());
        // 4. 设置参数
        //  获取到了参数的全路径
        String paramterType = mappedStatement.getParamterType();
        Class<?> paramTypeclass = getClassType(paramterType);
        List<ParameterMapping> parameterMappingList = boundSql.getParameterMappingList();
        for(int i=0;i<parameterMappingList.size(); i++){
            ParameterMapping parameterMapping = parameterMappingList.get(i);
            String content = parameterMapping.getContent();
            // 反射
            Field declaredField = paramTypeclass.getDeclaredField(content);
            // 暴力访问
            declaredField.setAccessible(true);
            Object o = declaredField.get(params[0]);
            preparedStatement.setObject(i+1,o);
        }
        // 5.执行sql
        int resultSet = preparedStatement.executeUpdate();
        String resultType = mappedStatement.getResultType();
        Class<?> resultclassType = getClassType(resultType);
        // 存储结果容器
        Object result = new Object();
        // 封装返回结果集
        Object o = resultclassType.newInstance();
        if(resultSet>0){
            o=1;
        }else {
            o=0;
        }
        return (T)o;
    }

    @Override
    public <T> T insert(Configuration configuration, MappedStatement mappedStatement, Object... params) throws ClassNotFoundException, IllegalAccessException, NoSuchFieldException, Exception {
        return execute(configuration,mappedStatement,params);
    }

    @Override
    public <T> T update(Configuration configuration, MappedStatement mappedStatement, Object... params) throws ClassNotFoundException, IllegalAccessException, NoSuchFieldException, Exception {
        return execute(configuration,mappedStatement,params);
    }

    @Override
    public <T> T delete(Configuration configuration, MappedStatement mappedStatement, Object... params) throws ClassNotFoundException, IllegalAccessException, NoSuchFieldException, Exception {
        return execute(configuration,mappedStatement,params);
    }

    private Class<?> getClassType(String paramterType) throws ClassNotFoundException {
        if(paramterType !=null){
            Class<?> classl = Class.forName(paramterType);
            return classl;
        }
        return null;
    }

    /**
     *  完成 对 #{}的解析工作，1. 将#{} 使用？ 进行代替，2. 解析出#{}里面的值进行存储。
     * @param sql
     * @return
     */
    private BoundSql getBoundSql(String sql) {
        // 标记处理类，配置标记解析器来完成对占位符的解析处理工作
        ParameterMappingTokenHandler parameterMappingTokenHandler = new ParameterMappingTokenHandler();
        GenericTokenParser genericTokenParser = new GenericTokenParser("#{","}",parameterMappingTokenHandler);
        // 解析出来的sql
        String parseSql = genericTokenParser.parse(sql);
        // #{} 里面解析出来的参数
        List<ParameterMapping> parameterMappings = parameterMappingTokenHandler.getParameterMappings();
        BoundSql boundSql = new BoundSql(parseSql,parameterMappings);
        return boundSql;
    }

}
